Method of and apparatus for drying motor compressors

ABSTRACT

The invention relates to a method and apparatus for drying motor compressors of the type having a semispherically shaped casing with a motor compressor unit mounted in the casing. The drying object is achieved by introducing, under pressure, a directed stream (or streams) of a gaseous drying medium into the gap between the wall of the case and the motor compressor unit at several peripheral points and the internal curvature of the casing causes the streams to respectively leave the gap at other peripheral points.

United States Patet H91 in] 3,72%,832 Load 5] May 1, 1973 [54] METHQD OF AND APPARATUS FOR 2,644,188 7/1953 Pacilio ..34/105 X DR MOTOR COMPRESSORS 2,509,396 5/1950 Mayer ..34/l04 [75 Inventor: Egon Lund, Sonderborg, Denmark [73] Assignee: Danfoss A/S, Nordborg, Denmark [22] Filed: May 12, 1971 21 Appl. No.: 142,554

FOREIGN PATENTS OR APPLICATIONS 123,769 lO/l9l9 Great Britain ..34 /lO4 Primary ExaminerCarroll B. Dority, .Ir. Att0rney-Wayne B. Easton 5 7 ABSTRACT The invention relates to a method and apparatus for drying motor compressors of the type having a semispherically shaped casing with a motor compressor unit mounted in the casing. The drying object is achieved by introducing, under pressure, a directed stream (or streams) of a gaseous drying medium into the gap between the wall of the case and the motor compressor unit at several peripheral points and the internal curvature of the casing causes the streams to respectively leave the gap at other peripheral points.

7 Claims, 4 Drawing Figures [30] Foreign Application Priority Data May 5, 1970 Germany ..P 20 21 948.1

[52] US. Cl. ..34/34, 34/105, 34/222, 34/224 [51] Int. Cl ..F26b 3/00 [58] Field of Search ..34/22, 30, 31, 34, 34/104, 105, 225, 222

[56] References Cited UNITED STATES PATENTS 2,385,962 10/1945 Barnett ..34/IO5 X [i l f- 1/ f N U M i If 5+ Own r7 @1 mew 1 5 J 1i Patented May 1, 1973 2 Sheets-Sheet 2 METHOD OF AND APPARATUS FOR DRYING MOTOR COMPRESSORS The invention relates to a method of drying motor compressors that are fitted in a case that is still open, and to apparatus for performing this method.

As far as possible, all moisture should be removed from encased motor compressors used in refrigerating equipment, since water, by forming ice, can interrupt the refrigerant circuit and can reduce the service-life of the machine because of corrosion and the like. Motor compressors must therefore be intensively dried before the case is closed.

In the past such compressors have been dried in a normal drying oven, the motor winding optionally undergoing additional electrical heating. The drying time lasted several hours however, so that the drying process either could not be incorporated in the production line at all, or, if it were, only ifa great deal of space were occupied.

It has been possible to reduce the drying time to approximately 90 minutes by passing the units first through perchlorethylene vapor and then through air. The perchlorethylene condensed on the motor compressor and displaced the moisture, and was driven off by the subsequent treatment in air. The use of perchlorethylene however calls for certain safety measures.

The object of the invention is to enable motor compressors to be dried without the use of perchlorethylene, and further to reduce the drying time.

According to the invention, this object is achieved by introducing, under pressure, a directed stream of gaseous drying medium into the gap between the wall of the case and the motor compressor and at several peripheral points, and causing it to leave the gap again at another peripheral point.

The various peripheral points are thus swept by a very strong induced stream of drying medium, in particular a strong stream of hot air. An intensive drying action is obtained since fresh drying medium, that is able to absorb moisture to a large extent, is passed over each of the various peripheral points, and since the drying medium rapidly moves past the points to be dried and is then discharged, so that no appreciable abatement of the drying action due to saturation with moisture occurs. In this way, the time required for drying a normal motor compressor can be reduced to about minutes. The space required for carrying out the drying operation in a production line is correspondingly small.

It is particularly expedient if the drying medium is introduced at several peripheral points in succession. With this arrangement, a relatively great length of gap is in each case available for the flow of the drying medium supplied. Furthermore, the continuous change in the course of the stream safely prevents the creation of zones ofstagnating drying medium.

It is thus possible to confine the point at which the stream of drying medium enters to one peripheral portion of the gap and to move this point ofentry along the periphery and relatively to the case. A further possibility which is particularly suitable in the case of continuously operating production lines is that of alternately applying the action of two streams of drying medium, the entry points of which are each confined to one peripheral portion of the gap, to opposite sides of the periphery.

According to the invention, apparatus for performing this method and comprising a drying chamber, with an inlet and outlet, for accommodating at least one case together with the motor compressor, is characterized by a nozzle arrangement fitted in the drying chamber and directed into the gap between the wall of the case and the motor compressor, and by an arrangement for providing relative movement between the nozzle arrangement and the case.

In a production line, it is very advantageous if the nozzle arrangement is fixed and the arrangement for imparting movement is a conveyor belt. In particular, the nozzle arrangement consists of individual nozzles or sets of nozzles disposed alternately on both sides of the cases carried on the belt. The cases, moving along on the belt, are then alternately charged with the drying medium at opposite peripheral points.

In a preferred embodiment, the drying chamber is a substantially horizontal duct, the height and width of which only slightly exceed the corresponding dimensions of the open case and of the motor compressor. The small volume of the duct ensures that the drying medium emerging from the case can be quickly removed by suction.

Suction orifices are preferably provided in that surface of the duct opposite the nozzle arrangement, these orifices being distributed over the length of the duct. The suction orifices can also take the form of a slot. In this way, at most only a very small part of the drying medium supplied through the nozzle arrangement is enabled to circumvent the case and flow directly towards the suction orifice.

It is also of advantage if the cases are open at the top, and the nozzle arrangement is fitted on the top wall of the duct and the suction orifices on the base thereof below the nozzle arrangement. The cases can then simply be placed on a conveyor belt.

In a preferred arrangement, several ducts each containing a conveyor belt are arranged side-by-side. In this arrangement, the advantages accruing when only one duct is used are still present, but the lagging of the drying apparatus is very considerably reduced. Losses due to radiation are low. A compact and shorter drying apparatus results.

A very simple construction results if a pressure chamber is provided on the top wall of the duct, and nozzle pipes, projecting into the pressure chamber, are fitted in the lower wall of this chamber. This ensures that nozzle pipes of sufficient length can be used so as to produce the required directed flow yet without the nozzle pipes projecting into the duct where they could impede movement.

Also, the vacuum chamber can be provided on the bottom of the duct, and the suction orifices, preferably in the form of a continuous slot, can be contained in the upper wall of the suction chamber. If the pressure and vacuum chambers are associated with the duct in this manner, several ducts can be readily arranged side-byside.

In a further construction in accordance with the invention, there are provided at both ends of the duct discharge conduits, communicating with. the atmosphere, for marginal losses of drying medium; a

recycling pipe with a multi-stage high-pressure blower for the main part of the drying medium and connecting the vacuum chamber to the pressure chamber; and a pipe for supplying fresh drying medium and comprising a quantity-regulating device, this pipe running into the recycling pipe upstream of the blower and heating apparatus. Part of the moisture is carried away each time with the marginal losses. The recycled and supplemented drying medium can be so treated by the application of heat that is enabled to absorb moisture again.

In another construction, the nozzle arrangement can be fitted on a rotatable plate, the axis of which is aligned with the axis of the case. By rotating the nozzle arrangement relatively to the plate, the peripheral portion at which the drying medium enters can be continuously changed.

The invention will now be described in more detail by reference to embodiments illustrated in the drawing, in which:

FIG. 1 is a schematic longitudinal section through drying apparatus in accordance with the invention,

FIG. 2 is a plan view of the conveyor belt with the nozzle arrangements located above it,

FIG. 3 is a cross-section through part of the one embodiment of the apparatus, and

FIG. 4 is a schematic cross-section through a second embodiment of the apparatus.

In the drying apparatus seen in FIGS. 1 3, a conveyor belt 1, driven by way of rollers 2 and 3, runs through a drying duct 4. Cases 5, which are still open and which each contain a motor compressor 6, are carried on the conveyor belt. Provided on the top wall ofthe duct is a pressure chamber 7 in which nozzle pipes 8 are so arranged that their outlet orifices are disposed at the same level as the top wall of the duct 4. Provided below the duct is a vacuum chamber 9, which communicates through a slot 10 with the duct 4. The entire system is surrounded by thermal lagging 11.

A recycling conduit 12 runs from the vacuum chamber 9 to a multi-stage blower 13, which passes circulated air through a heating apparatus 14 into the pressure chamber 7. At the inlet and outlet of each duct are located discharge conduits 15, through which marginal losses of drying air are passed to the atmosphere. Fresh supplementary air is passed in through a supply pipe 16 containing a quantity-regulating device 17. It can be expected that 5 percent of the drying air is discharged through the conduits 15, 95 percent of the air is recycled, and thus 5 percent of fresh air is brought into the system.

As shown in FIG. 2, the nozzle pipes 8 are arranged in groups 18 and 19, which are alternately arranged on the two sides of the cases 5 carried on the conveyor belt. When the case is beneath the group 18, as shown on the left in FIG. 3, the pressure-directed drying air enters the gap between the case S and the motor compressor 6 at the peripheral point a. The air flows through the case roughly in the direction indicated by arrows and is discharged through the slot 10 into the vacuum chamber 9. As shown on the right in FIG. 3, air then passes from the group 19 of nozzles into the gap between the case 5 and the motor compressor 6 at the peripheral point b, and flows through the case, again in the direction indicated by the arrows. In this way, an intensive drying action is applied alternately from both sides.

FIG. 3 shows that the cross-section of the ducts only slightly exceeds that of the case and the motor compressor incorporated therein. Here, the rollers 2 of the conveyor belt 1 can be driven through a common shaft 20. The pressure chambers 7 have a common connection 21, and the vacuum chambers 9 a common connection 22.

In one construction used on a practical basis, four ducts 4 were arranged side-byside. Each had a length of 3 meters. The conveyor belt moved at a speed of 9 meters per hour, so that the cases left the duct in the dried condition after 20 minutes. The nozzle pipes had a diameter of approximately 8 mm and were approximately 60 mm long. The air was introduced into the pressure chambers 7 at a temperature of roughly 170C. If percent of the air is recycled and only 5 percent of fresh air is supplied, this temperature corresponds to a dew-point of approximately minus 40C. The blower pressure was so selected that a pressure differential of about 1,300 mm water column obtained between the pressure chamber and the vacuum chamber.

FIG. 4 shows another embodiment in which a drying chamber 23 is surrounded by lagging 24. A case 5 remains stationary on the bottom of the chamber 23. A

plate 25 is rotated by a shaft 26, which is co-axial with I the case 5. The plate 25 carries a nozzle pipe 27 which is supplied with hot air through a passage 28 in the shaft 26. Suction orifices 29 in the bottom of the chamber 23 lead to a vacuum chamber 30. A feed orifice 31 is contained in the end wall.

Here, a stream of air is passed from the nozzle 27 into the gap between the case and the motor compressor, the point of introduction being continuously displaced over the periphery.

Air can also be directed simultaneously at several peripheral points into the gap between the case and the motor compressor. The air then passes out again between these points of entry. Instead of supplying the air alternately on the two sides as illustrated in FIGS. 1 to 3, or instead of the continuous displacement of the point of entry as shown in FIG. 4, use can be made of other ways of supplying the air, for example, at three or four different peripheral points in succession.

I claim:

1. A method for drying a motor compressor assembly of the type having a generally semispherically shaped casing with a motor and compressor unit mounted therein comprising the step of directing a stream of gaseous drying medium so as to enter into the circumferential space between said unit and the internal surface of said case at one peripheral point and to ieave said circumferential space at another diametrically opposite peripheral point.

2. A method according to claim 1 wherein at least one more stream similar to said stream is provided and said streams are successively directed into and out of said casing.

3. A method according to claim 2 wherein said streams are positionally arranged so that opposite sides of a casing are alternately subjected to said streams.

4. A method according to claim 2 wherein assemblies similar to said assembly are moved on a conveyor through a drying chamber and a stationary nozzle arrangement for delivering said streams of gaseous drying medium is provided.

7. A method for drying a motor compressor assembly of the type having a generally semispherically shaped casing with a motor and compressor unit mounted therein comprising the step of directing a steam of gaseous drying medium so as to enter into the circumferential space between said unit and the internal surface of said case at one peripheral point and to leave said circumferential space at another peripheral point,

said stream moving in a circular path about the axis of said casing. 

1. A method for drying a motor compressor assembly of the type having a generally semispherically shaped casing with a motor and compressor unit mounted therein comprising the step of directing a stream of gaseous drying medium so as to enter into the circumferential space between said unit and the internal surface of said case at one peripheral point and to leave said circumferential space at another diametrically opposite peripheral point.
 2. A method according to claim 1 wherein at least one more stream similar to said stream is provided and said streams are successively directed into and out of said casing.
 3. A method according to claim 2 wherein said streams are positionally arranged so that opposite sides of a casing are alternately subjected to said streams.
 4. A method according to claim 2 wherein assemblies similar to said assembly are moved on a conveyor through a drying chamber and a stationary nozzle arrangement for delivering said streams of gaseous drying medium is provided.
 5. Drying apparatus for drying motor compressor assemblies of the type having a generally semispherically shaped casing with a motor and compressor unit mounted therein comprising a conveyor belt, a drying chamber duct surrounding said belt having a height and width which only slightly exceeds the corresponding dimensions of said casings and sets of nozzles for directing streams of gaseous drying medium arranged alternately on opposite sides of said belt.
 6. Apparatus according to claim 5 wherein said nozzles are positioned above said belt and suction orifices are in said duct beneath said belt.
 7. A method for drying a motor compressor assembly of the type having a generally semispherically shaped casing with a motor and compressor unit mounted therein comprising the step of directing a steam of gaseous drying medium so as to enter into the circumferential space between said unit and the internal surface of said case at one peripheral point and to leave said circumferential space at another peripheral point, said stream moving in a circular path about the axis of said casing. 